A vibration feeding apparatus typically comprises a container in the form of a rotary vibration bowl and a linear feeder in the form of a vibratory track. They can be found in industry for conveying and orienting components, for instance electronic components, which are delivered in bulk to the vibration feeding apparatus during mass production. They are different from belt conveyers in that vibratory feeding apparatus use small vibrations to transfer components in a step-wise manner. Due to its simplicity and lack of moving mechanical parts, the vibratory feeding apparatus can provide a cleaner and more reliable way of conveying small components. Thus, there are large numbers of vibratory feeding apparatuses developed for conveying small components in different industries.
A vibration feeding apparatus generally involves four main mechanical modules: a bowl or track for orientation and sorting, a hopper for refilling the bowl or track, linear and/or rotary vibrator modules for exciting the bowl, track and/or hopper to vibrate, and a platform for vibration isolation.
The linear or rotary vibrator module generally excites the bowl or track to undergo vibration with a single frequency. The vibrator module comprises a movable block that transmits vibration to the bowl or track, an actuator that provides excitation forces to the movable block, and a spring-mass system that determines the vibration frequency of the vibrator and the conveyance direction. The vibrator module may include an electromagnetic solenoid, such that the force-displacement relationship of the vibrator module is non-linear in nature. The force from the solenoid accelerates the bowl or track to vibrate and the components placed on the bowl or track experience acceleration. The resultant acceleration has both vertical and horizontal components. When the vertical acceleration field is slightly larger than the gravitational field, the components are lifted off the bowl or track surface and are projected forward due to the horizontal acceleration component.
The vibration feeding system also comprises a vibratory bowl container. There are helical chute grooves inside this container for conveying electronic components from a bottom of the bowl to an outlet at a top of the bowl. The electronic components should preferably be aligned to a specific orientation before they are delivered to the outlet of the bowl. A conventional approach is to discard electronic components with incorrect orientations by generating a rejection signal using a sorting sensor and then returning incorrectly-oriented electronic components back to the bottom of the container for recycling. However, the result is that fewer electronic components will be delivered to the outlet of the bowl and this approach yields a lower feed rate and efficiency. The vibratory bowl needs to speed up considerably to compensate for those electronic components which have to be recycled through such rejection by generating a higher vibration level. Disadvantageously, a higher vibration level will lead to component bouncing that also limits the feeding speed due to electronic components having shorter contact times with the chute grooves.
The conventional approach has further limitations in relation to electronic components which have unique orientations and need many passes of orientation checking and rejection. The number of correctly-oriented components delivered to the bowl outlet will be decreased significantly. For such applications, double or even more helical grooves, rejection and merge systems are necessary, such that the bowl container design becomes more sophisticated and difficult for fabrication and set-up.
In U.S. Pat. No. 6,513,644 entitled “Apparatus and Method for Aligning Parts”, a part-holding chamber has an arc-shaped chute groove for orienting electronic components in a given direction and a gate port which allows electronic components in a correct orientation to pass through in a single line. A rotary impeller having blades is mounted to urge any electronic components at the gate port that are in an incorrect orientation away from the direction in which electronic components are discharged to prevent clogging. However, a limitation of this design is that the electronic components have to be symmetrical in shape without requiring top and bottom orientation or arrangement in order to be aligned by the part-holding chamber.
Moreover, in U.S. Pat. No. 7,810,632 entitled “Vibratory Conveying Apparatus”, the apparatus as described therein sorts out and rejects electronic components with incorrect orientations but does not attempt to change the orientations of the components during sorting. The efficiency of the apparatus is thus low with many of the electronic components being automatically rejected, and the feed rate is limited.